Boron removal from synthetic wastewater by adsorption onto bone char
wastewater treatment; boron; adsorption; bone char
Boron is an essential micronutrient for plants, humans and animals, which is also an important component used in various industries. Along with the widespread of boron application, more and more boron waste pollutes the drinking water sources, and leads to a series of environment and health problems. Boron contaminations are aggravated by the fact that it cannot be removed by conventional water treatments and its separation still remains an issue. In this context, the goal of this paper was to explore boron removal in a synthetic effluent through the adsorption process in bovine bone char. Design of experiments was carried out using the Central Composite Design (CCD). Optimization was carried out by Generalized Reduced Gradient (GRG) and Normal Border Intersection (NBI) methods. At initial effluent pH of 7.72, solid-liquid ratio of 59.95 gbone char.kg-1effluent and an initial boron concentration of 18.63 mg.L-1, it was possible to reach 43% of boron removal, with a variance of 2%². Steam pre-treatment for bone char was also evaluated and neither caused significant structural changes in the adsorbent nor influenced the adsorption of boron. The equilibrium study showed that Freundlich and Henry models described better the system, compared to Langmuir, Temkin and Langmuir-Freundlich isotherms, suggesting a reversible process. Pseudo-second order adsorption kinetics model best fitted experimental data and the thermodynamic parameters revealed an endothermic (ΔH = +15.17 kJ.mol-1), spontaneous and controlled by entropy (ΔS = +0.07 kJ.mol-1.K-1) process.